[Amps] 4-1000 amp

[Chris Pedder]

At 09:29 29/05/2006, R.L. Measures wrote:

>   The 3-1000Z has a grid that does a marginal job of shielding the
>input from the output -- which means it has more feedback-C than need
>be.  The 3cx1200A7 is the external anode version of the 3-1000Z and
>it apparently uses the same grid and filament.  Both tubes have a
>reputation for squirreliness -- especially with higher anode PS
>voltages.  Eventually, Eimac discontinued making the 3-1000Z and the
>3cx1200A7 evolved into the 3cx1200Z7, which has less feedback-C --
>and better stability.  Unfortunately, the ...A7 and the ...Z7 are not
>interchangable.

I cannot help but wonder why you keep pedalling this one. I have 
been, yet again, to the Eimac/CPI data sheets which read as follows:


grounded grid capacitance in pf

                      in          out          feedback
3CX1200A7            20          10.3          0.6
3CX1200Z7            17.6         9.7          0.8

This does not accord with your comments. Are the Eimac figures incorrect?

Chris